/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using Checksum = SupportClass.Checksum;
using CRC32 = SupportClass.CRC32;

namespace Lucene.Net.Store
{

    /** Writes bytes through to a primary IndexOutput, computing
     *  checksum as it goes. Note that you cannot use seek(). */
    public class ChecksumIndexInput : IndexInput
    {
        IndexInput main;
        Checksum digest;

        public ChecksumIndexInput(IndexInput main)
        {
            this.main = main;
            digest = new CRC32();
        }

        public override byte ReadByte()
        {
            byte b = main.ReadByte();
            digest.update(b);
            return b;
        }

        public override void ReadBytes(byte[] b, int offset, int len)
        {
            main.ReadBytes(b, offset, len);
            digest.update(b, offset, len);
        }

        public long GetChecksum()
        {
            return digest.getValue();
        }

        public override void Close()
        {
            main.Close();
        }

        public override long GetFilePointer()
        {
            return main.GetFilePointer();
        }

        public override void Seek(long pos)
        {
            throw new System.SystemException("not allowed");
        }

        public override long Length()
        {
            return main.Length();
        }
    }
}
